Electric communication system



June 30, 1942. A. ROSEN ELECTRIC COMMUNICATION SYSTEM Filed April 7, 1941 2 SheetsSheet l [PI/V I I w H TTORNEY,

June 30, 1942. A. ROSEN 2,288,487

ELECTRIC COMMUNICATION SYSTEM Filed April '7, 1941 2 Sheets-Sheet 2 6 554, Ross v 9 "rToR/YEK Patented June 30, 1942 ELECTRIC COMMUNICATION SYSTEM Abel Rosen, London, England, assignor to Siemens Brothers & Co., Limited, Westminster, London, England, a British company Application April 7, 1941, Serial No. 387,223 In Great Britain June 15, 1939 9 Claims.

The present invention relates to electric communication systems of the kind in which an unattended repeater such as a submerged repeater at an intermediate point in a submarine cable is supplied with power current over the transmission circuit from a source at a control point such as a terminal station. By power current is meant current which provides the power for energizing the amplifying equipment of the repeater. Such current is of course quite distinct from the communication currents.

According to one feature of the invention, in a system in which power current is thus fed to an unattended repeater; the repeater is arranged so that it on the cessation of the receipt of power current assumes a circuit condition in which the amplifying equipment is disconnected and the transmission circuit is switched straight through via a metallic circuit. For the arrangement to be a practical one, the method of carrying out a the feature must be such as to render it possible for the normal operative condition to be readily established in the absence of a fault in the transmission circuit or repeater.

The provision of the feature referred to is especially advantageous in the case where the unattended repeater is a submerged repeater at an intermediate point in a submarine cable, as in this case the possibility of setting up at will a through transmission circuit without amplifying equipment and with no feed or control current passing over the cable conductor or conductors renders possible the carrying out of routine dielectric and conductor tests and facilitates the process of locating faults in the cable. The arrangement of course also serves to provide means whereby faulty repeater apparatus can be cut out of the transmission circuit to provide continuity of service. The metallic circuit referred to may simply comprise one or more direct through connections via back contacts of a control relay, or may include a winding of a control relay. We prefer to employ the first of these two arrangements.

The above-mentioned and other features of the invention are exemplified in the two specific submarine cable systems embodying the invention which will now be described with reference to the accompanying drawings. In the drawings, Fig. 1 illustrates the arrangements in one system and Fig. 2 illustrates the arrangements in the other system.

Referring firstly to the system of Fig. l, the submarine cable system in question consists of two concentric cables, each serving for one direction of transmission of a two-way transmission system. The two transmission paths of the twoway transmission system are arranged similarly, and therefore for simplicity only the arrangements concerned in the provision of one path are shown in the drawing.

One of the two concentric cables of the cable system is shown diagrammatically in the figure and designated CC. The cable does not run uninterruptedly between the cable terminal stations TW and TE but is divided into three sections by two submerged repeaters RW and RE. The submerged repeaters are of course suitably housed in watertight containers. Repeater RW is energized by alternating current supplied from terminal station TW, and repeater RE is energized by alternating current supplied from terminal station TE. The frequency of the alternating current supplied from the terminal stations is lower than the lowest frequency of the communication currents transmitted over the system.

When repeaters RW and RE are in the normal operative condition, control relays SW and SE are held in the operated condition and the transmission path provided by cable CC passes (going from left to right) over a high-pass filter I-IPTW, a test key KW in its unoperated position, the lefthand section of the cable, a high-pass filter HPRW, an amplifier VRW, the central section of the cable, an amplifier VRE, a high-pass filter HPRE, the right-hand section of the cable, a test key KE in its unoperated position, and a high-pass filter HPTE. It must, of course be understood that, although the transmission path has just been traced going from left to right, the actual direction of transmission that is provided for (by an appropriate connection of the amplifiers) will depend upon which particular one of the two concentric cables of the cable system is concerned.

All the filters and amplifiers employed in the system are of the kind in which one input terminal and one output terminal are directly connected together (or are in actual fact formed by a single common terminal) and in the drawings the diagrammatic representations employed to show the filters and amplifiers are designed to bring out this fact.

At the terminal station TW, the arrangements are such that when key PW is operated and key- KW is not operated, as is normally the case, power current for repeater RW is applied to the two conductors of cable CC. The power current is derived from an alternating current source GW and is fed to the cable via a low-pass filter LPTW. The high-pass filter HPTW prevents power current from flowing to the communication circuit connected to the left-hand terminals of this filter, and is designed so that it performs this filtering action without unduly shunting away current from source GW. The object of the low-pass filter LPTW is to prevent communication currents from being shunted away via source GW. Filters HPTW and LPTW are naturally designed to have cut-off frequencies which lie between the frequency of the alternating power current and the lowest frequency of the communication currents it is desired to transmit. When the test key KW is operated the central conductor of the cable is disconnected from filters HPTW and LPTW and connected via the left-hand one of test Wires WW to a circuit arranged for the carrying out of routine dielectric and. conductor tests and of tests for locating faults in the cable.

The arrangements at the terminal station TE correspond exactly to those at station: TW, there being associated with cable CC a high-pass filter I-IPTE, a low-pass filter LPTE, a test key KE controlling the connection of the central cable conductor to the relevant one of Wires WE leading to a testing circuit, a source GE of power current for repeater RE, and a key PE controlling. the connection of source GE to the cable.

Considering now the arrangements at repeater RW, during normal operation power current received over the left-hand section of the cable is fed to the primary winding of a power transformer XW via a circuit comprising contact $1113 and a low-pass filter LPRW. The object of filter LPRW is to prevent communication currents from being shunted away via the branch circuit containing the power transformer. The power current is prevented from reaching and affecting amplifier VRW by a high-pass filter I-IPRW, which is designed so that it performs its filtering action without unduly shunting power current away from the branch circuit just referred to. Like filters HPTW and LPTW, filters HPRW and LPRW are designed to have cut-off frequencies which. lie between the frequency of the alternating. power current and the lowest frequency of the communication currents it is desired to transmit. Condenser QW is an isolating condenser which will be referred to later. It and an associated spark quench resistance YW are short-circuited by contact sw3 when the repeater is in the normal operative condition. The secondary of the power transformer XW is connected to feed current to'a control relay arrangement which may conveniently consist of a control relay SW of ordinary electromagnetic type in series with a dry-plate rectifier DW, the relay being shunted by a reservoir condenser EW. The holding of relay SW in the operated state is thus effected by a portion of the current received from source GW. The secondary of transformer XW is also connected to feed rectifying apparatus UW which is connected to provide the power for the valves of the amplifier VRW'. When the power supply for the repeater is cut off at terminal station TW or otherwise, the control relay SW is de-energised and releases, so that at contact sw3 the short-circuit across isolating condenser QW and resistance YW is opened and at contacts swl and sw2 the central conductor of the left-hand section of the cable is connected straight through to the central conductor of the central section. Such release of relay SW would usually be caused by the restoration of key PW or the operation of the test key KW. The isolating condenser QW has a capacity which is high enough to allow sufficient current to pass to operate relay SW when the power supply is re-applied but is low enough to prevent the branch circuit containing the power transformer from seriously affecting the carrying out of dielectric tests on the cable.

The arrangements at repeater RE correspond exactly to those at repeater RW, there being associated with cable CC an amplifier VRE, a highpass filter HPRE, an isolating condenser QE, a spark quench resistance YE, a low-pass filter LPRE, a power transformer XE, a control relay SE, a dry-plate rectifier DE, a reservoir condenser EE, and rectifying apparatus UE.

The frequency of the power current supplied by the sources GW and GE may be of the order of 50 cycles per second and the communication currents may have frequencies from 300 cycles per second upwards. The isolating condensers QW and QE may each have a value between 1 and 10 microfarads, the value used in any particular case being as small as is possible consistent with the proper control of the relevant control relay. The value of each of resistances YW and YE may be ohms.

It will be clear to those skilled in the art that control relay arrangements generally similar to those which have just been described may be employed in the case where one cable is used for both directions of transmission and a two-way repeater at an intermediate point in the cable is supplied with alternating power current over the transmission circuit.

Referring now to the submarine cable system illustrated in Fig. 2, this is a system in which a single concentric cable CC serves for both directions of transmission of a two-way transmission system. Different frequency bands are used for the two directions of transmission. As in the case of the system of Fig. 1, the cable is divided into three sections by two submerged repeaters. The drawing shows one terminal station TW and the repeater (designated RW) which is the nearer to this station. Repeater RW is energised by direct current supplied from terminal station TW. fhe other repeater and terminal station are respectively similar to RW and W and are correspondingly arranged, and need not therefore be illustrated or described. The circuits shown in Fig. 2 are arranged on the assumption that the lower of the two frequency bands referred to is used for transmission in the right to left direction. This band (lower band) is not amplified in the two submerged repeaters but the other band (upper band) is amplified by the amplifiers such as VRW. In so far as transmission over the sections of the cable itself is concerned, the upper band is attenuated more than the lower band, and the amplifiers are designed to render the overall transmission efficiency of the cable system the same for both bands.

When repeater RW is in the normal operative condition, control relay SW is held in the operated condition and the transmission path provided by the part of the system shown in the drawing for the lower band of communication currents passes over the central section of the cable, a low-pass filter LBRW, the left-hand section of the cable, and a test key KW in its unoperated position. The corresponding transmission path for the upper band of communication currents passes over the test key KW in its unoperated position, the left-hand section of the cable, a high pass filter UBRW, an amplifier VRW, and the central section of the cable. The filters LBRW and UBRW are suitably designed to keep the lower and upper bands in their proper paths at repeater RW. They are also designed so that they do not provide any path for direct current from battery BW.

As in the case of the system of Fig. 1, all the filters and amplifiers employed in the system are of the kind in which one input terminal and one output terminal are directly connected together (or are in actual fact formed by a single common terminal).

At times when repeater RW is in the normal operative condition, power current from battery BW at station TW is received at the repeater and fed to a potentiometer resistance YPW via a circuit comprising a low-pass filter LPRW, contact 81123, and the winding of the control relay SW. The fiow of the power current through the relay Winding holds the relay operated. The control relay is of the slow-to-release type. The power for one or more valves of the amplifier VRW is derived from a tapping or tappings on potentiometer YPW. At times when power current is being fed to repeater RW, the conditions at terminal station TW are that the test key KW is not operated and that a three-position switch PW is operated to complete a circuit over its lower fixed contact. The connection of battery BW to the cable conductors is effected via a low-pass filter LPTW. This filter and filter LPRW at the repeater are designed to prevent communication currents from being shunted away via the power supply equipment. Ihe said two filters must of course be of a kind adapted to permit the passage of direct current.

When the power supply for the repeater RW is cut off at terminal station TW or otherwise, the control relay SW is de-energised and releases, so that at contact sw3 the direct-current circuit comprising the relay winding and potentiometer YPW is opened and at contacts swl and sw2 the central conductor of the left-hand section of the cable is connected straight through to the central conductor of the central section. Such release of relay SW would usually be caused by the placing of switch PW in its central position or the operation of the test key KW. Condenser QW is an isolating condenser which becomes effective in the circumstances now being considered, and which has a capacity low enough to prevent the branch circuit which passes over filter LPRW, spark quench resis ance YW, primary winding of transformer XW, and potentiometer YPW from seriously affecting the carrying out of dielectric tests on the cable. Such tests would normally be carried out via the wires WW at station TW, which are connected to a circuit arranged for the carrying out of routine dielectric and conductor tests and of tests for locating faults in the cable.

In order to establish the normal operative condition subsequent to the cutting off of the power current, switch KW is restored if operated and switch PW is first operated to complete a circuit over its upper fixed contact and is then switched over rapidly to complete the circuit over its lower fixed contact. Switch PW may actually have any form adapted to permit switching over at the requisite speed. When switch PW is operated to complete the circuit over its upper fixed contact,

current from an alternating source GW is fed to the cable conductors of the left-hand section of the cable and this current flows at repeater RW in the alternating current circuit which passes over low-pass filter LPRW, condenser QW, resistance YW, primary winding of transformer XW, and parallel-connected resistance YPW and condenser QPW. It may not be absolutely necessary to provide condenser QPW in some particular cases, but we normally prefer to provide such a condenser in order to reduce the impedance of the alternating current circuit just referred to. The output from the secondary of transformer XW is rectified by the rectifying arrangement formed by dry-plate rectifier DW and reservoir condenser EW, and serves to operate the control relay SW. As soon as contact 8203 closes, direct current from battery BW flows through the winding of relay SW, and this condition naturally persists after switch PW has been switched over rapidly to complete the circuit over its lower fixed contact and thus to complete the desired establishment of the normal operative condition. It should be noted that the rectifier DW is so connected that the direct current supplied from it to relay SW is in the same direction as that supplied from battery BW. The rectifier also prevents current from battery BW from flowing via the secondary winding of transformer XW.

The frequency of the alternating current supplied by the source GW may be of the order of 50 cycles per second and the communication currents may have frequencies from 300 cycles per second upwards. Condenser QW may have a value between 1 and 10 microfarads and resist ance YW may be ohms.

What is claimed is:

1. An electric communication system comprising atransmission circuit, a repeater situated at an intermediate point along said transmission circuit, said repeater comprising thermionic valve equipment, a source of electric current at one terminal end of said transmission circuit for the operation of said repeater over said transmission circuit, terminal means at each end of said transmission circuit for the communication currents, and means associated with and at said repeater responsive to the operating current for said repeater and operating automatically on the connection of said source to said terminal end for switching said repeater into said transmission circuit.

2. An electric communication system comprising a transmission circuit, a repeater situated at an intermediate point along said transmission circuit, said repeater comprising thermionic valve equipment, a source. of electric current at one terminal end of said transmission circuit for the operation of said repeater over said transmission circuit, terminal means at each end of said trans-- mission circuit for the communication currents, and means associated with and at said repeater responsive to the operating current for said repeater and operating automatically on the connection of said source to said terminal end for switching said repeater into said transmission circuit and for switching said transmission circuit directly through on disconnection of said source from said terminal end.

3. An electric communication system comprising a transmission circuit, a repeater situated at an intermediate point along the transmission circuit, said repeater comprising thermionic valve equipment, a source of alternating electric current atone terminal end of said transmission circuit for the operation of said repeater over said transmission circuit, the frequency of alternation being lower than the lowest frequency present in the communication currents, terminal means at each end of said transmission circuit for the communication currents, and means associated with and at said repeater responsive only to said operating current of lower frequency and operating automatically on the connection of said source of lower frequency alternating current to said terminal end for switching said repeater into said transmission circuit.

4. An electric communication system comprising a transmission circuit, a repeater situated at an intermediate point along the transmission circult, said repeater comprising thermionic valve equipment, a source of alternating electric current at one terminal end of the transmission circuit for the operation of said repeater over said transmission circuit, the frequency of alternation being lower than the lowest frequency present in the communication currents, terminal means at each end of said transmission circuit for the communication currents, and means asscciated with and at said rep-eater responsive only to said operating current of lower frequency and operating automatically on the connection of said source of lower frequency alternating current to the terminal end for switching said repeater into said transmission circuit and for switching said transmission circuit directly through on disconnection of said source from said terminal end.

5. An electric communication system comprising a transmission circuit, a repeater situated at an intermediate point along said transmission circuit, said repeater comprising thermionic valve equipment, a source of alternating electric current at one terminal end of said transmission circuit for the operation of said repeater over said transmission circuit, the frequency of alternation being lower than the lowest frequency present in the communication currents, terminal means at each end of said transmission circuit for the communication currents, means at the said repeater for separating the operating current for the repeater from the communication currents, and means responsive to such separated operating current and operating automatically on the connection of said source to the terminal end for switching said repeater into said transmission circuit.

6. An electric communication system comprising a transmission circuit, a repeater situated at an intermediate point along said transmission circuit, said repeater comprising thermionic valve equipment, a source of alternating electric current at one terminal end of said transmission circuit for the operation of said repeater over said transmission circuit, the frequency of alternation being lower than the lowest frequency present in the communication currents, terminal means at each end of said transmission circuit for the communication currents, means at the said repeater for separating the operating current for the repeater from the communication currents, and means responsive to such separated operating current and operating automatically on the connection of said source to the terminal end for switching said repeater into said transmission circuit and for switching said transmission circuit directly through on disconnection of said source from said terminal end.

'7. An electric communication system comprising a transmission circuit, a repeater situated at an intermediate point along said transmission cricuit, said repeater comprising thermionic valve equipment, a source of direct current at one terminal end of the transmission circuit for the operation of said repeater over said transmission circuit, a source of alternating current at said one terminal end, means for connecting in succession the sources of alternating and direct current to said transmission circuit, and means situated at said repeater initially operable automatically on the connection of said source of alternating current to said terminal end for switching said repeater into said transmission circuit, said means being maintained operated by the connection of the source of direct current at said terminal end, following the disconnection of the source of alterating current.

8. An electric communication system comprising a transmission circuit, a repeater situated at an intermediate point along said transmission circuit, said repeater comprising thermionic valve equipment, a source of direct current at one terminal end of said transmission circuit for the operation of said repeater over said transmission circuit, a source of alternating current at said one terminal end of said transmission circuit, the frequency of alternation being lower than any 1' requency present in the communication currents, switching means at said repeater for switching said repeater into said transmission circuit, filter apparatus at said repeater connected to said transmission circuit permitting passage of said alternating current and direct current, transforming and rectifying apparatus utilising alternating current flowing through said filter apparatus and providing direct current for initially operating said switching means on the connection of said source of alternating current at said terminal end, said switching means on operation further switching itself directly in series with said filter apparatus and when not operated switching the transmission circuit directly through.

9. An electric communication system according to claim 8 wherein said switching means comprises a slow releasing relay, an operating circuit therefor including in series said filter apparatus, a condenser and the primary winding of a transformer, the secondary winding of which is connected through a rectifier to the relay winding, contacts for said relay which when unoperated connect the transmission circuit directly through and which when operated switch said repeater into the transmission circuit, further contacts which when operated bridge the relay winding across said primary winding and condenser.

ABEL ROSEN. 

